Computer systems generally utilize auxiliary memory storage devices having media on which data can be written and from which data can be read for later use. A direct access storage device (DASD) such as a disk drive incorporating rotating magnetic disks is commonly used for storing data in magnetic form on the disk surfaces. Data is recorded on concentric, radially spaced tracks on the disk surfaces, and magnetic heads are used to write the data to and read the data from the tracks on the disk surfaces.
Data is written onto a disk by a write head that includes a magnetic yoke having a coil, passing there through. When current flows through the coil, a magnetic flux is induced in the yoke, which causes a magnetic field to fringe out at a write gap. It is this magnetic field that writes data, in the form of magnetic transitions, onto the disk.
FIGS. 1-2 illustrate a method of manufacturing a coil structure associated with a magnetic head, in accordance with the prior art. FIG. 1 illustrates a cross-sectional view of an initial stack 100 with which a prior art coil structure may be manufactured. As shown, the stack 100 includes a first layer 102 including Al2O3 or some other substrate material. Deposited on the first layer 102 is an adhesion layer 104, which could be Cr or the like. A thin seed layer 106 is deposited on the second layer 104. The third layer 106 is constructed from a conductive material such as Cu or the like and can be deposited by sputtering.
On the third layer 106 is a fourth layer 108 including masked photoresist that defines a helical channel, 110, shown in cross section in FIG. 1. This channel 110, defines a coil structure. Deposited in the channels 110 is a conductive material 111 such as Cu or the like, which can be deposited by electroplating. After the conductive material layer 111 has been deposited, the photoresist can be removed and a material removal process or processes such as etching or ion milling can be used to remove any conductive material remaining between the turns of the coil.
The above processes result in a coil having a certain aspect ratio A/B. As will be appreciated by those skilled in the art, ever increasing data rate and data capacity requirements require ever increasing write fields from ever smaller write heads. The challenge therefore, in designing write coils is to increase the aspect ratio of the write head in order to increase the number of coil turns that can be fit into a given write head yoke. Ideally the spacing between turns of a coil should be minimized as much as possible while avoiding shorting between adjacent coils. In the above process, the photoresist defines the space between adjacent coils. However, photolithographic processes as well as the material properties of the photoresist, severely limit the amount by which this spacing can be reduced.
More recently, in an effort to minimize spacing between coils, a damascene process has been used to construct a coil having a smaller pitch than was previously possible using conventional processes. Such a damascene process is described in patent application U.S. 2003/0184912, filed April, 2002. With reference to FIGS. 3 and 4, a photoresist layer 404 is deposited on top of a substrate 402. Magnetic pedestal layers 405, and magnetic back gap (not shown) are formed adjacent to the coil structure to provide a portion of the magnetic pole and yoke structure for the write head, and can be constructed of, for example NiFe. An insulating fill material 407 such as alumina Al2O3 is deposited in the field area such adjacent beyond the pedestal, beyond the back gap (not shown) and into the plane of the paper (not shown). A hard mask 406, such as SiO2 is deposited. Then a photoresist layer 410 is deposited and patterned to define the coil structure having multiple turns. With reference to FIG. 4, a reactive ion etching process is then performed to form a deep high aspect ratio channel 412.
With reference now to FIG. 5, a Ta barrier layer 502 may then be deposited, followed by a Cu seed layer 504. Then, with reference to FIG. 6, Cu is electroplated 602, to completely fill the channels 412 and cover the previously deposited layers.
With reference now to FIG. 7, one or more CMP processes would then be desirable to remove upper portions of the copper 602, patterned photoresist 410, SiO2 hard mask 406, Ta barrier layer 502 as well as the NiFe pole portions 405, and alumina Al2O3 fill material 407. However, previously available CMP processes remove the different materials at different rates. For example, such CMP processes remove alumina faster than the other deposited materials such as NiFe or Cu, leading to unacceptable recession 702 of the alumina. For example, such recession has typically caused a step height 704 of about 0.8-0.9 micrometers between the NiFe portions 405 and the Alumina fill 407. Furthermore, such CMP processes cause severe corrosion of the NiFe portions such as the pedestal 405 and back gap (not shown) as well as the coil 602. Because of these challenges previous attempts to commercialize such a damascene process have experienced limited success.
Therefore, there remains a need for a material removal process that can remove all of the above materials simultaneously, resulting in planar surface. Such a process would preferably consist of as few separate processing steps as possible and would not cause corrosion of any of the deposited layers.